The present invention relates to the testing of rail in track by means of ultrasonic energy, and more particularly is concerned with a track testing carriage that permits the proper positioning of the ultrasonic sensing means as progressive testing of successive portions of the rail occurs.
The inventors have found that the prior art ultrasonic inspection systems, such as embodied in U.S. Pat. No. 3,028,751, did not provide the necessary precision control for adjusting and maintaining the ultrasonic apparatus with the necessary degree of orientation relative to the rails.
The testing of rail in-track by means of ultrasonic energy requires that the orientation of the ultrasonic beams with respect to the rail be maintained with some precision while the test vehicle moves along the rail at a variable speed. Specifically certain beams directed at an angle with respect to the vertical must be generally parallel to the longitudinal center line of the rail and in some cases coincident with the vertical center line of the rail cross section. A beam directed to impinge vertically on the base of the rail must be so centered and kept perpendicular to the base thereof.
Generally the distance from the gauge or inside edge of the rail head to the vertical center line of the rail section remains constant over considerable distances along the track but may vary by reason of differences in rail section or due to wear of the rail head. Accordingly to obtain the desired precision testing data, it is necessary to maintain the horizontal position of the ultrasonic transducer with respect to the rail section while being able to vary that position at will, and to maintain the angular position of the ultrasonic transducer with respect to the rail axis constantly, as well as with respect to the vertical axis of the section and to vary same at will.
The two rails of a given track, except as they may be out of repair, are parallel to each other and proceed in straight lines except where intentionally curved. When negotiating such curves or testing along straight stretches of track, the parallelism between the transducer beams and the rail axes and hence with each other is to be maintained, this generally in spite of variations in the gauge (distance between the rail heads) and variations in the straightness of one or both rails. To accomplish these functions the inventors have devised an ultrasonic track testing carriage which provides freedom of motion either voluntarily, or automatically in some senses, while resisting motion in others to obtain the necessary echo signals.